CH3COOH(acetic acid) cannot reduce Fehling solution whileHCOOH,HCHOand CH3CHOreduce Fehling solution due to the presence ofCHOgroup.

Reduction of Fehling's solution

Fehling's solution is a chemical reagent used to test for the presence of reducing sugars. When heated with a reducing sugar, such as glucose or fructose, it is reduced to form a red precipitate of copper(I) oxide.

The reduction of Fehling's solution can be carried out by various reducing agents such as aldehydes, ketones, and some acids. However, one of the following cannot reduce Fehling's solution.

Option B: Acetic acid

Acetic acid is a weak acid and cannot reduce Fehling's solution. It does not contain a carbonyl group that can be oxidized or reduced. Therefore, it cannot react with Fehling's solution to produce a red precipitate.

On the other hand, the other options can reduce Fehling's solution as follows:

Option A: Formic acid

Formic acid is an aldehyde that can be oxidized to form carbon dioxide and water. It can react with Fehling's solution to produce a red precipitate.

Option C: Formaldehyde

Formaldehyde is also an aldehyde that can react with Fehling's solution to produce a red precipitate.

Option D: Acetaldehyde

Acetaldehyde is an aldehyde that can be oxidized to form acetic acid. It can react with Fehling's solution to produce a red precipitate.

Conclusion

In conclusion, acetic acid cannot reduce Fehling's solution because it does not contain a carbonyl group that can be oxidized or reduced. The other options can reduce Fehling's solution because they contain aldehydes that can react with Fehling's solution to produce a red precipitate.

CH3COOH (acetic acid) cannot reduce Fehling solution while HCOOH, HCHO and  CH3CHO reduce Fehling solution due to the presence of CHO group.